Any index - unique or non-unique, sorted order or Metamorph - can be
eliminated if it is no longer needed. The DROP INDEX command is
used to remove an index. The format of this command is similar to the
DROP TABLE command illustrated in Chapter here.

DROP INDEX index-name ;

Example:
Let's say the DEPTINDEX is no longer needed. Delete it with this
statement:

DROP INDEX DEPTINDEX ;

The table on which the index was created would not be touched.
However, the index created for it has been removed.